Machines for compression molding closure shells, or compression molding sealing liners within closure shells, typically include a turret or carousel that rotates around a vertical axis. A plurality of molds are provided around the periphery of the turret, in the form of male and female mold sections that are aligned along vertical axes parallel to the axis of turret rotation. Cams drive one or both of the mold sections of each pair between an open position, in which a molded part is stripped from the mold and a charge of molten plastic material is placed into the mold, and a closed position in which the mold sections are brought together to compression mold the shell or liner. In a liner machine, premade shells are placed in a nest when the mold sections are open, and a charge or pellet of liner material is placed within the mold before the mold is closed. U.S. patents that illustrate machines of this type for compression molding plastic closure shells include U.S. Pat. Nos. 5,670,110, 5,989,007, 6,074,583 and 6,478,568. U.S. patents that illustrate machines of this type for compression molding sealing liners within closure shells include U.S. Pat. No. 5,451,360. U.S. application Ser. No. 11/109,374 discloses a vertical wheel compression molding machine, which rotates around a horizontal axis, for compression molding closure shells or sealing liners within closure shells.
The present disclosure involves a number of aspects that can be implemented separately from or in combination with each other.
An apparatus for severing mold charges of molten plastic exiting an orifice along an orifice axis, in accordance with one aspect of the present disclosure, includes a motor system that provides a rotary output around an axis offset from the orifice axis. A blade arm is eccentrically coupled to the rotary output of the motor system for motion in a plane at an angle to the orifice axis, preferably perpendicular to the orifice axis. A knife blade is coupled to the blade arm and disposed to oscillate in a closed path, preferably an elliptical path, that intersects the orifice axis so that the knife blade engages and severs molten plastic exiting the orifice along the orifice axis. A control arm preferably is pivotally coupled to the blade arm and to a point that is fixed with respect to the orifice axis to control motion of the blade arm and the knife blade. The motor system preferably is mounted on a base, and has an output shaft that extends through the base and a hub coupled to the output shaft. The blade arm is pivotally coupled to the hub eccentrically of the shaft. The knife blade preferably has a cutting edge that is at an angle to the blade arm.